How long is the tip in contact with the cue ball?Clips HSV A.77-A.81 and A.147-A.151 (external web-link) show close-ups of cue tip impact for various hardness tips and various speeds. Here are some conclusions:

most contact times (i.e., for most tips and most speeds) are very close to a thousandth of a second (0.001 sec).

a soft tip at slow speed has a longer contact time (about 0.002 sec), but still extremely small.

a very hard tip (phenolic) at fast speed has a shorter contact time (about 0.0005 sec).

the contact time decreases slightly for faster speeds, but not by much.

chalk does not stay on hard tips very well at impact (see the blue clouds that separate from the tips in the videos).

For some super-super-slow motion videos and data for how contact time varies with cue speed, see DBKcue's page on this topic. (external web-link)Some people think that what they do with their grip hand or follow through can change the tip contact time, but this is not the case (i.e., it is not possible to get a significant effect). Also, some people think a softer tip, which has a slightly longer contact time, can create more CB "reaction." This is not the case. The peak force isn't as large with a longer contact time (i.e., the force is spread out over a longer time). Therefore, the "hit" might "feel" slightly different to the player. However, the momentum effects (cue and ball speed changes) will still be the same, assuming the tips being compared have the same efficiency. Another thing that might be different is that a shorter contact time is usually associated with a harder tip, and a harder tip might have better efficiency, so the CB might have slightly more speed and spin with a harder tip for a given cue mass and speed. For more info and resources on these topics, see:tip hardness effectscue tip efficiencycue "hit," "feel" and "playabilityeffects of light vs. tight gripstroke accelerationfollow throughfrom Patrick Johnson:Longer contact time might increase spin a tiny amount (because the tip rotates a tiny bit farther from center during contact), but not enough to matter - probably not even a noticeable amount.

But longer contact time cannot decrease squirt. In fact, if it increases spin a tiny amount, it also increases squirt a tiny amount.

The bottom line is that increased contact time, even if we could somehow change our stroke to make it happen (which we can't), wouldn't make any significant difference anyway.

How much does the tip deform during contact with the cue ball?Here's an image from some high-speed video filmed by a group from Austria:

The full video clip can be viewed at HSV A.76 (YouTube) (it is the third clip in the sequence). The video was shot at 2000 frames per sec with a high-resolution color camera. Here's an isolated clip of the close-up of the tip contact:

I've collected a sequence of images from the video clip and have made them available in MS Word (Download) and PDF (Download) formats. The MS Word file is large (1.7 MB), but it is very useful. If you page down through the file to load all of the images, you can then use the scroll bar to simulate a flip-book animation. The faster you scroll, the faster the simulated "video" plays. The images are 1/2000 second (0.0005 or 5 ten-thousandths of a second) apart.Here are some observations, insights, and questions from the collection of stills:- The tip is probably relatively soft based on the contact time and amount of deformation. Contact lasts about 4 frames (over frames 3-6), which corresponds to about two thousandths (0.002) of a second.- The cue tip seems to stay in contact with the ball as the ball starts to rotate, which might contribute to the amount of cue stick deflection.- The cue tip had an excessive amount of chalk on it (as evidenced by the pre-impact chalk trail through the air and by the huge chalk cloud after impact).Here's another excellent video showing the tip dynamics during contact:

Is it important to remove the mushroomed edges of a tip?If your tip is properly shaped tip and you are hitting the cueball within the non-miscue zone, the extreme edge of the tip doesn't come into play (e.g., see the diagrams in "Draw Shot Primer - Part VII: tips of english" (Download) - BD, July, 2006).However, removing the mushroomed edges does:

make the tip look prettier, and it might be less visually distracting to some.

feel better if you happen to pull the tip back through your bridge during your stroke (which isn't recommended).

What affects how well a tip delivers speed to the cue ball?A hard tip will create slightly more CB speed for a given cue speed. For more info, see:

from Mike Page:Given that the speed of sound in maple is 4100 m/s, I'm wondering if break cue manufacturers are barking up the wrong tree going to harder and harder tips.

Presumably the motivation for going to hard tips--phenolic or whatever--is a belief that they are more efficient in the way you describe above.

An unintended consequence, though, of these hard tips may be that because the contact time is shorter, there may not be enough time for the ball to "see" the full mass of the stick.

4100 meters/sec is 4 meters per millisecond. A round trip for the compression wave is about 3 meters (two stick lengths). So it takes about three quarters of a millisecond for the cueball to even have a chance of knowing about the back of the stick.

My guess is the contact time for break tips is in that range.

Why not try an efficient soft tip? Maybe get the contact time up to 1.2 ms or more?dr_dave's reply:The harder tips are more efficient (see HSV B.42 - tip and cue efficiency, with Bob Jewett). (YouTube)My best measurements for phenolic tip contact time gave values close to 1/2 ms, but I didn't test at break speed. For more info, see: Cue Tip Contact TimeExcellent points and questions. Anecdotally, it seems like the phenolic tips still provide an advantage over softer tips, which currently all seem to be less efficient.

How much force is generated between the tip and the cue ball during a break shot, and what would it take to generate a "ton" of force at the tip?To keep things simple, let's use a cue weight of 18 oz and assume a perfect tip with a center-ball hit. For this case, TP A.30 (Download) predicts that the outgoing CB speed is about 3/2 (1.5) the incoming cue speed. Let's also assume that the average force during tip contact is about half the peak force. And let's assume the tip is in contact with the ball for 0.001 sec, which is typical.

Does the tip hardness affect how much english can be applied, or the amount of squirt that results?Here are some relevant factors:

A hard tip holds its shape better over time, in general.

Tip hardness (within the typical range) should not have a significant or direct effect on the amount of english that can be applied.

The amount of english is limited by the tip offset that creates a miscue.

A tip not "treated" (e.g., scuffed) properly, will not hold chalk very well, and miscues will be more likely at smaller tip offsets. A harder tip might require more attention in this regard.

Soft tips seem to hold chalk better than hard tips, in general.

A soft tip will give the cue a softer "feel" (less impact in grip hand) and have a different sound than a hard tip. Some people prefer some sounds and "feels" more than others. For more info, see cue "hit," "feel," and "playability."

Some people think that because a soft tip stays in contact with the CB slightly longer (see contact time), a soft tip can apply more english. However, see Bob Jewett's comments below. Also, the contact time is still extremely small with both a soft and hard tip: close to a thousandth of a second (0.001 sec). Assuming the CB speed is the same in all comparisons: even though the peak force will be different (more with the shorter contact time), the amount of momentum (linear and angular) transferred to the CB will still be the same (because the sum of force over contact time is the same in both cases). The CB doesn't move much (translation or spin) during the extremely small contact time, so the only significant factor is the tip contact point at impact.On a different note, a hard tip will create slightly more CB speed for a given cue speed (see tip efficiency). Some people also prefer a hard tip because they "feel" the force of the shot better (a softer tip dampens the impact a little).There are many factors related to tip hardness that could influence squirt, including: tip density/weight, tip efficiency, contact time, and effective endmass. "Return of the squirt robot" (Download) (BD, August, 2008) documents an experiment related to the effects of tip hardness on squirt. A softer tip did seem to create slightly more squirt, but the experiment was not very well controlled (see the article (Download) for more info). In general, if the contact time is longer (as is the case with a softer tip), the effective endmass and resulting squirt should be larger (see the rubber-super-ball-tip report (external web-link) as an example). Another set of more careful experiments documented in the Cue and Tip Testing for Cue Ball Deflection (Squirt) video (YouTube) and “Cue Tip Squirt Testing” (Download) (BD, June, 2014). seem to imply that tip type, hardness, and height have very little effect on shaft squirt. Among the wide range of tips tested in the video (YouTube), the harder tips did result in slightly more squirt. This makes sense because the harder tips are denser and heavier, creating more "endmass." The shorter contact time seems to be less of a factor than the added weight.Another factor involved with a softer tip is that it might better absorb glue and adhere to the ferrule more strongly and making it less likely to come off with lots of use and/or abuse.from Mike Page:Here's one more. Even if soft and hard tips held chalk exactly the same, it's possible the soft tip might reduce the chance of miscue. For instance, suppose a miscue occurs when less than 50% of the contact patch has chalk. If the bald regions are small, then this standard may be violated more frequently for a hard tip with its small contact patch.from Bob Jewett:One issue is which harness of tip will allow the farther-from-center hit. Some believe that a soft tip takes chalk better so it can hit the ball farther from center.There is a counter theory, and that is because a softer tip will have a longer contact time than a hard tip. During contact, the tip rides around the side of the ball some, so the final eccentricity as the tip leaves the ball is larger than when the tip first hits the ball. A softer tip, with the longer contact time will be farther off center at the end than a harder tip with the same starting offset. If both tips can only hold to a certain point of offset, and you start your shot so the miscue point is barely reached at the end of contact, the average offset will be larger for the harder tip. This means that the harder tip can create more spin for a given ball speed.Which dominates? Holding chalk better or starting farther off-center? I don't know of any experiment that has tested this.

How do you replace the tip on a cue?The following videos demonstrate the process and tools needs to replace a cue tip:cue tip replacement (Seyberts) (YouTube)replacing a cue tip (Home Billiards) (YouTube)

Does the tip and shaft size and shape make a difference?For applying english, a smaller-diameter and rounder tip (approximately dime radius) is generally recommended. Here are some possible reasons:

The smaller, rounder shape allows for a more uniform contact area as the tip offset is increased. If you have The Illustrated Principles of Pool and Billiards (external web-link), this is illustrated in Figure 2.2 on pg. 18. This could help make miscues less likely at large tip offsets.

For shots with english, the impact is more centralized to the core of the cue for a smaller, rounder tip. This might result in a better "feel" for some people with firm shots. Also, it has been suggested by Predator (external web-link) that a centralized hit helps reduce squirt. It certainly is true that if you remove more material by rounding the tip down to a dime, you might reduce endmass and squirt. Also, there might be less sideways tip and shaft flex with a more centralized hit, which could have an effect (see what causes squirt for more info).

One advantage of a flatter tip is that a center-ball hit, with some tip placement inaccuracy, will generally have less unintentional english (and unexpected throw). In other words, a larger, flatter tip is more "forgiving" with near-center-ball hits. It is also easier to control small amount of sidespin since more cue offset is required to create more sidespin, as compared to a rounder tip.Here's an expanded diagram from "Squirt - Part VI: tip shape" (Download) (BD, January, 2008) that illustrates tip shape effects:

Another concern related to shaft diameter is bridge comfort. With a closed bridge, some shaft sizes and tapers will be more comfortable than others to different individuals. This is less of a concern with an open bridge.The shaft size and tip shape can also influence how some people apply english if they use "tips" of english and/or an aim-and-pivot squirt compensation system (e.g., BHE). This might make some people think they are getting more or less english with different size and shape tips. For more info, see "Squirt - Part VI: tip shape" (Download) (BD, January, 2008).Tip shape can also affect the results of squirt-testing machines that position the shaft and CB the same with each test. If the tip shape is different from one shaft to the next, the effective tip offset will be different, creating a slightly different amount of squirt, with everything else being equal. This could have an adverse effect on squirt-testing results. In comparing shafts, identical tips should be used. Each shaft should be tested with the same tip size, shape, height, hardness, and weight.from Patrick Johnson (from AZB post): (external web-link)

(Click to enlarge)

(The diagram above) shows four tips touching the cue ball at 30 degrees offset from center (about halfway from center to edge), which is about where the miscue limit is no matter what the size or shape of your tip.

There are two shaft diameters shown: top = 12.75mm; bottom = 10mm.There are two tip shapes shown: left = nickel radius; right = dime radius.

As you can see, the larger diameter shaft (at top) contacts the cue ball farther from its edge at the miscue limit, and there's room at the edge of the tip to spare with either tip shape. This is because a 60-degree arc (30 degrees in each direction) on a nickel or dime radius is smaller than 12.75mm wide.

The smaller diameter shaft (at bottom) still has a small amount of room at the edge of the tip with the dime shape, but is right on the edge with the nickel shape. This is because a 60-degree arc (30 degrees in each direction) on a nickel radius is just about 10mm wide and on a dime radius it's just a little less than 10mm wide.

Conclusions:- Nickel or dime radius only makes a difference on very small diameter tips.- On very small tips it's better to have a dime radius than a nickel radius.